1. Technical Field
The invention relates to aerial refueling systems, whereby a first aircraft may refuel a second aircraft during flight.
2. Background Art
Aerial refueling is a common method for extending the flight time and range of an aircraft and typically involves a tanker aircraft, which is loaded with excess fuel, transferring fuel to one or more trailing or receiver aircraft.
One known type of refueling system is the "boom"-type disclosed in U.S. Pat. No. 2,663,523. In this system, a rigid refueling boom pivotally mounted beneath the tail of the aircraft is deployed downwardly to a receiver aircraft which is positioned behind and beneath the tanker. An operator located within the tanker controls the movement of the boom relative to the tanker aircraft so as to direct its free end into a refueling port on the receiver aircraft. The boom is often provided with an aerodynamic profile which serves both to facilitate positional control and lower resulting drag loads during refueling operations.
One drawback of known boom-type systems is that the boom must be permanently incorporated within the structure of the aircraft, thereby implicating substantial aircraft alternations to the aircraft not otherwise amenable to temporary installations. Moreover, such known boom type systems reduce the ground clearance in the region of the aircraft tailcone and, hence, limit the amount of aircraft rotation available for take-off and landing maneuvers. A reduced amount of available rotation in turn reduces the angle of attack of the aircraft's wings and, hence, the generated lift by a corresponding amount, with the net result being a significant reduction in the operational payload capability of the aircraft. The payload reduction is most severe when modern transport aircraft utilizing wings with high lift devices are burdened with the envelope of such known, aft-mounted refueling booms.
An alternate type of refueling system is disclosed in U.S. Pat. No. 3,008,674. In this system, a detachable refueling pod is mounted beneath the main wing of the tanker aircraft. A hose is deployed from the aft portion of the refueling pod, whereupon a stabilizer drogue attached to the hose's trailing end facilitates interconnection with the receiving aircraft. In a variation on this theme, U.S. Pat. No. 5,667,170 teaches mounting such a detachable refueling pod to either side of the aircraft fuselage between the main wings and the aft stabilizers, such that, when deployed, each pod's respective refueling hose is channeled away from the aircraft fuselage, with the further benefit of reducing the maximum loads applied to the wing otherwise encountered when refueling with wing-mounted pods.
However, such trailing hose refueling systems, whether wing-mounted or fuselage-mounted, continue to suffer from a lack of positive control over the motion of the drogue and the trailing end of the refueling hose. The situation is further complicated by the airflow over the wing and fuselage during flight.
Accordingly, what is needed is a detachable aerial refueling system which advantageously employs a boom for added control and reduced aerodynamic drag, without suffering payload capacity penalty of known boom-type systems.